[C++知识库]Angr安装与使用之使用篇（十二）

针对angr提供的17道练习题，现在进行求解11_angr_sim_scanf，它也是关于hook输入的问题，需要使用angr求解出正确密码。但是需要提供排除地址以减少路径求解时间。
具体代码如下所示

import angr
import claripy
import sys

def main(argv):
  path_to_binary = argv[1]
  project = angr.Project(path_to_binary)

  initial_state = project.factory.entry_state()
  #定义一个类，它继承angr.SimProcedure
  class ReplacementScanf(angr.SimProcedure):
    #使用此函数替代输入函数
    def run(self, format_string, scanf0_address, scanf1_address):
      scanf0 = claripy.BVS('scanf0', 32)
      scanf1 = claripy.BVS('scanf1', 32)

      #输入函数会将用户输入写入到缓冲区中
      self.state.memory.store(scanf0_address, scanf0, endness=project.arch.memory_endness)
      self.state.memory.store(scanf1_address, scanf1, endness=project.arch.memory_endness)
      
	  #位向量scanf0及scanf0是类ReplacementScanf的局部变量，需要使用globals将这两个符号位向量变为全局变量
      self.state.globals['solution0'] = scanf0
      self.state.globals['solution1'] = scanf1

  #使用具体符号名定位到需要hook的函数位置
  scanf_symbol = '__isoc99_scanf'
  project.hook_symbol(scanf_symbol, ReplacementScanf())

  simulation = project.factory.simgr(initial_state)

  def is_successful(state):
    stdout_output = state.posix.dumps(sys.stdout.fileno())
    return b'Good Job.' in stdout_output

  def should_abort(state):
    stdout_output = state.posix.dumps(sys.stdout.fileno())
    return b'Try again.' in stdout_output

  simulation.explore(find=is_successful, avoid=should_abort)

  if simulation.found:
    solution_state = simulation.found[0]

    # 获取位向量scanf0及scanf0
    stored_solutions0 = solution_state.globals['solution0']
    stored_solutions1 = solution_state.globals['solution1']
    
    solution0 = solution_state.solver.eval(stored_solutions0)
    solution1 = solution_state.solver.eval(stored_solutions1)

    print('solution are: {0},{1} '.format(solution0,solution1))
  else:
    raise Exception('Could not find the solution')

if __name__ == '__main__':
  main(sys.argv)

下面验证实验结果
执行刚刚写好的程序，保存为scaffold11.py，并将其与11_angr_sim_scanf放于同一文件夹中，具体如下图所示。

再执行11_angr_sim_scanf，然后需要我们输入angr刚刚求解出的密码，结果为Good Job。

至此，求解11_angr_sim_scanf已全部完成。